Motion pictures, broadcast television programs, and videos rendered on video-display devices provide to a viewer the illusion of continuous motion by rapidly displaying a sequence of still images. The still images are referred to as “frames.” When a sufficient number of frames are displayed per second, the human visual system fills in the time gaps between successive frames to create the illusion of continuous motion. Motion pictures display 24 frames per second, with a 1/30 second interval between frames, analog television displays 30 frames per second, or, equivalents, 60 interleaving fields per second, and future high-definition television (“HDTV”) standards are expected to specify a frame-display rate of 60 frames per second.
While, in general, the illusion of continuous motion generated by display of a sequence of still frames allows humans to watch and enjoy motion pictures and television broadcasts, the illusion of continuous motion provided by motion pictures and television broadcasts is not perfect. Certain artifacts and annoyances arise from the discontinuous nature of motion pictures, television, and video display, collectively referred to as “video display” in this document. One exemplary artifact is that, in television broadcast of old western movies, the wheels on covered wagons and carriages occasionally appear to move backwards when the carriages and covered wagons are moving forward and the rotation of the wheels, in revolutions per second, is slightly slower than the frame capture rate of the motion-picture camera. An example of an annoyance that arises from the discrete nature of video display is the perceptible flicker of cathode-ray-tube-based television displays and computer monitors.
As video-display devices have improved, over the years, and evolved from analog devices to digital devices, video-display devices have become capable of providing higher display rates, including display rates that are higher than the frame-capture rates at which video frame are recorded and transmitted through various broadcast and electronic or optical data-transmission media. Increased display rates generally provide a better illusion of continuous motion with fewer artifacts and annoyances. However, implementations of video-display devices capable of these higher frame-display rates may be substantially more complex and expensive. For this reason, designers and manufacturers of various types of video-display devices strive to increase frame display rates while minimizing increases in hardware complexity and implementation cost.